1. Field of the Invention
The present invention relates to a pico-cell indicator to be installed at predetermined positions for easy cell-registration in case that a mobile station is moving from a micro-cell service area to a pico-cell service area and a method for cell registration of mobile station by using the pico-cell indicator according to a certain code signal which is generated in the pico-cell indicator.
2. Description of the Conventional Art
In general, in order to increase traffic capacity in a service area, a cell, which is in a service area, is divided into mega-cells, the mega-cells are divided into macro-cells, the macro-cells are divided into micro-cells and the micro-cells are divided into pico-cells, so that it becomes possible to easily provide communication service even in a densely populated area or a high building.
When a mobile terminal shifts between the service areas, the service is maintained by registration-change from a current registered cell into a larger cell, as the number of registration event which generates per a unit time period exceeds a predetermined frequency. On the other hand, the service is maintained by registration-change from a current registered cell into a smaller cell, as the number of registration event which generates per a unit time period is short of the predetermined frequency.
For example, if a user enters a building, the service area is changed from the micro-cell to the pico-cell and at this time, the time for changing the service area should be minimized in order to prevent waste the source of the system.
However, the conventional technique has a disadvantage that such a change of service areas takes a certain time necessarily and is not performed at the same time with the shift of the mobile terminal between the service areas, thereby resulting in the waste of wireless sources.
The present invention is derived to resolve the disadvantages of the conventional techniques, and it is an object of the present invention to provide a pico-cell indicator and a method for cell registration of mobile station by using the pico-cell indicator, wherein the pico-cell indicators are installed at the entrances of buildings or parking lots to transmit a certain key signal representing pico-cell with a predetermined time interval and a terminal of a mobile communication system receives the signal to change the registration of service area of the mobile system from a micro-cell to a pico-cell rapidly, so that phasing area is minimized to effectively use the system and the waste of the wireless sources is prevented.
In order to achieve the above objects of the present invention, according to one aspect of the present invention, a pico-cell indicator includes a means for generating a predetermined code signal for indicating pico-cell, a modulator for modulating the code signal output from the code signal generating means into pseudo noise PN code for code division multiple access CDMA communication, a mixer for mixing the PN code which is modulated by the modulator with a carrier signal which is output from a local oscillator, and an RF transmitting means for transmitting the mixed signal output from the mixer through an antenna after converting the mixed signal into an RF signal.
Also, according to another aspect of the present invention, a method for cell registration of a mobile terminal by using a pico-cell indicator includes the steps of determining whether a code signal of the pico-cell indicator is received when the mobile terminal is not engaged, determining whether a timer in the mobile terminal is in operation when the code signal of the pico-cell indicator is input by the mobile terminal, storing a current micro-cell ID and registering the pico-cell when the timer is not in operation, preparing the micro-cell ID which is registered before the pico-cell when the timer is in operation and registering the micro-cell as the operation of the timer is finished, determining whether a code signal from the pico-cell indicator is received when the mobile terminal is engaged in the first step, determining whether the engagement is finished by determining when the code signal is input by the mobile terminal, and setting the timer and storing the micro-cell when the engagement is finished and registering the pico-cell as the operation of the time, is finished.